There’s nothing more dispiriting than that (sometimes inevitable) slow slide back into weight gain after working for months in the gym and kitchen to build a leaner and stronger body. However, keeping those calories down while adhering to HIIT can prevent those pounds from piling back on, says a new study published in the American Journal of Physiology.

"One of the major problems when you restrict calories on a diet is that you lose muscle mass, and as a result your metabolism slows down to accommodate the restriction of food," said study co-author Eric Plaisance, Ph.D., assistant professor of exercise science in the University of Alabama at Birmingham School of Education. "Eighty percent of people who lose weight by dieting gain all of it back in a four- to five-year period."

For the study, researchers wanted to find out what type of exercise could help preserve muscle mass and subsequently keep metabolism higher, so they turned to mice. They found that when the mice were on a calorie-restricted diet and performing HIIT they had better glucose and insulin tolerance, and didn’t lose as much lean body mass as the rodents on the same diet but doing moderate-intensity exercise.

"The No.1 reason that people tell us they do not exercise is due to a lack of time," said Plaisance. "High-intensity interval training takes about a third of the time as a continuous exercise training. If you are going to start a diet where you are restricting calories, these results could prevent muscle mass and maintain energy expenditure."